Electrochemical fluorination of 1,2-dichloroethane and 1,1,2-trichloroethane

ABSTRACT

In the electrochemical fluorination of 1,2-dichloroethane and 1,1,2-trichloroethane feedstocks, the selectivity to the products 1,2-dichlorotetrafluoroethane and 1,1,2-trichloro-1,2,2trifluoroethane is increased by charging a mixture of said feedstocks to the electrochemical fluorination cell instead of charging said feedstocks to the cell separately.

United States Patent inventor Appl. No. Filed Patented AssigneeELECTROCHEMICAL FLUORINATION 0F 1,2-

DICHLOROETHANE AND 1,1,2- TRICHLOROETHANE 8 Claims, 1 Drawing Fig.

[1.8. CI 204/59 Int. Cl 801k 3/00 Field of Search 204/59 TO ANODE BUS TOCATHODE BUS ELECTROLYTE LEVEL MAKE-UP HF [56] Reierences Cited UNITEDSTATES PATENTS 3,551,307 12/1970 Gray 204/59 3,298,940 l/l967 Ashley etal. 204/59 2,519,983 8/1950 Simons 204/59 Primary Examiner-John H. MackAssistant Examiner-Neil A. Kapian Attorney-Young and Quigg ABSTRACT: inthe electrochemical fluorination of 1,2- dichloroethane andl,l,2-trichloroethane feedstocks, the selectivity to the productsl,2-dichlorotetrafluoroethane and l,l,2-trichloro-i,2,2-trifluoroethaneis increased by charging a mixture of said feedstocks to theelectrochemical fluorination cell instead of charging said feedstocks tothe cell separately.

PRODUCTS SEPARATION ZONE MAKEUP HF PATENTEUunv 16 I9?! 3,620,941

PRODUCTS SEPARATION ZONE TO ANODE BUS T0 CATHODE BUS ELECTROLYTE LEVELINVENTOR.

F. N RUEHLEN my *I 4 A T TORNEYS ELECTROCHEMICAL FLUORINATION OF 1,2-DICHLOROETHANE AND 1 ,1 ,Z-TRICHLOROETHANE This invention relates to theelectrochemical fluorination of 1 ,2-dichloroethane and l ,1,2-trichloroethane.

Electrochemical fluorination processes for convening a wide variety offeedstocks into desirable fluorinated products are well known in theart. Generally speaking, these processes usually involve immersing anelectrode element in an electrolyte and passing an electric currentthrough said electrolyte between said electrode and an oppositelycharged element, e.g., either another electrode immersed in saidelectrolyte or the cell body which can serve as said other element. Thefeedstock to be fluorinated is then brought into contact with the anodeand at least partially converted at said anode, or in the regionthereof, into the desired product or products. In one electrochemicalfluorination process the feedstock is brought into contact with theanode by dissolving said feedstock in the electrolyte. In a variation ofthis process, the feedstock is bubbled into the electrolyte through aporous anode, such as porous carbon. Recently it has been discoveredthat the reaction in an electrochemical conversion process can becarried out within the confines of the porous electrode element itself,e.g., within the pores of said porous electrode. This type of operationis of particular utility in electrochemical fluorination. Carrying outthe fluorination reaction within the pores of a porous anode allowsoperation at higher rates of conversion, and without the formation ofsubstantial amounts of cleavage products generally produced by the oldermethods when operating at high conversion rates. The feed to befluorinated is introduced into the porous anode at a point near itsbottom and the fluorinated mixture exits at the top of the anode, orabove the electrolyte level or slightly below said level. Passage of thefeedstock into the bulk of the electrolyte is avoided.

Two valuable fluorinated compounds are l, l ,2-trichloro-1,2,2-trifluoroethane and l,2-dichlorotetrafluoroethane. Saidtrichlorotrifluoroethane is a valuable specialty degreasing solvent. Itis widely used, particularly in the aerospace industry, for cleaninginstruments, gears, and other parts which must be clean Said renderedespecially or grease-free. dichlorotetrafluoroethane is a valuableprecursor for, and can be readily converted to, tetrafluoroethylene.Said tetrafluoroethylene is an unsaturated fluorocarbon having valuableutility in various applications. One particular valuable utility is inthe form of its variouspolymers, several of which have achievedcommercial success. For example, the polymer of resin Teflon is widelyused as a coating material in many applications where a coating materialhaving release properties is desired, e.g., in the coating of cookingutensils. Teflon also has other well known utilities.

Both said 1,Z-dichlorotetrafluoroethane and said l,l,2-trichloro-l,2,2-trifluoroethane are produced when 1,2- dichloroethane iselectrochemically fluorinated; with the process being much moreselective to the production of said dichlorotetrafluoroethane. Both said1,2-dichlorotetrafluroethane and saidl,l,2-trichloro-l,2,2-trifluoroethane are also produced when saidl,l,2-trichloroethane is electrochemically fluorinated; with the processbeing much more selective to the production of saidtrichlorotrifluoroethane. Thus, if one were interested primarily in theproduction of 1,2- dichlorotetrafluoroethane, one could use1,2-dichloroethane as the feedstock. If one were interested primarily inthe production of 1,1 ,2-trichloro-1,2,2-trifluoroethane, one could usel,l,2-trichloroethane as the feedstock. However, problems areencountered in (l the efficient utilization of plant equipment, and (2the efficient utilization of said feedstocks, when one desires to makeboth of said products.

The present invention provides a solution to said problems. 1 have nowfound quite unexpectedly, that the overall yield of said productsl,2-dichlorotetrafluoroethane and l,l,2- trichloro-l ,2,2trifluoroethanei.e., the overall selectivity to the production of said products, can beincreased by charging both said 1,2dichloroethane and saidl,l,2-trichloro- 1.2,2trifluoroethane simultaneously as the feedstock tothe electrochemical fluorination cell. 1 have also found, quiteunexpectedly, that the efficiency of conversion of the 1,1,2-trichloroethane in the combined feedstock to the 1,1,2-trichloro-l,2,2-trifluoroethane product and its precursors is alsoincreased; and that this is accomplished without any significantsacrifice in the efficiency of conversion of the 1,2- dichloroethane inthe combined feedstock to the 1,2- dichlorotetrafluoroethane product andits precursors. l have further found that the ratio of said fluorinatedethane products produced in the cell can be varied by varying the ratioof said two feedstocks in the combined feedstock. Thus, in its broadestaspects, the present invention resides in the simultaneouselectrochemical fluorination of said two feedstocks so as to obtainincreased overall yield of, or overall selectivity to the production of,said products.

An object of this invention is to provide an improved electrochemicalfluorination process. Another object of this invention is to provide anelectrochemical fluorination process for the more efficient productionof l ,2- dichlorotetrafluoroethane and l ,1 ,Z-trichlorol ,2,2-trifluoroethane. Another object of this invention is to provide anelectrochemical fluorination process wherein the selectivity to theproduction of said 1,2-dichlorotetrafluoroethane andl,1,2-trichloro-l,2,2-trifluoroethane products is increased. Anotherobject of this invention is to provide an electrochemical fluorinationprocess wherein, by charging a mixture of l ,2- dichloroethane andl,l,2-trichloroethane to the electrochemical fluorination cell, there isobtained (1 increased selectivity to the production ofl,2-dichlorotetrafluoroethane and l,1,2-trichloro-1,2,2-trifluoroethane,and (2 increased efficiency in the conversion of saidl,l,2-trichloroethane. Other' aspects, objects, and advantages of theinvention will be apparent to those skilled in the art in view of thisdisclosure.

Thus, according to the invention, there is provided, in anelectrochemical fluorination process which comprises passing an electriccurrent through a current conducting essentially anhydrous liquidhydrogen fluoride electrolyte contained in an electrolytic cell providedwith a cathode and an anode, passing either (1 a feedstock comprisingl,l-dichloroethane or (2 a feedstock comprising l,l,2-trichloroethaneinto contact with said anode and fluorinating at least a portion of sameto fluorinated products including (a) l,l,2-trichloro-l,2,2-trifluoroethane and (b) l,2-dichlorotetrafluoroethane, and recoveringsaid products from a cell effluent stream, the improvement comprising:increasing the selectivity of said process to the production of saidproducts (a) and (b) by simultaneously passing said feedstocks (l and (2into contact with said anode and fluorinating at least a portion of sameto said products.

In the practice of the invention, the mole ratio of said two feedstocksin the combined charge to the cell can be varied over a wide range.Thus, said feedstocks can be charged in a mole ratio of1,1,2-trichloroethane to 1,2-dichloroethane within the range of 0.1:1 to20:1, preferably 0.221 to 10:1, more preferably 0.321 to 5:1. Generallyspeaking, increasing said ratio increases the production of l,l,2trichloro-l,2,2- trifluoroethane.

A number of advantages are realized or obtained in the practice of theinvention. These advantages are illustrated more specificallyhereinafter in connection with the examples. Said advantages include,among others, the following: (1 lncreased selectivity to the overallproduction of 1,2- dichlorotetrafluoroethane and l, l ,2-trich1orol,2,2- trifluoroethane. Thus, in the practice of the invention, theoverall yield of said two products is increased. (2 Increased efficiencyof conversion of l,l,2-trichloroethane without any significant sacrificein the efficiency of the conversion of 1,2- dichloroethane. (3 Moreefficient utilization of plant equipment including avoiding theinconveniences and complications of changing feedstocks, changingoperating conditions in the electrochemical fluorination cell, andchanging operating conditions in the separation equipment employed toseparate the cell products.

The invention is applicable to any electrochemical fluorination processwherein either l,2-dichloroethane or 1,1,2- trichloroethane is utilizedas a feedstock for the production of l ,2-dichlorotetrafluoroethane andl ,l ,2-trichloro-1 ,2,2- trifluoroethane. Thus, the invention isapplicable to electrochemical fluorination processes wherein thefeedstock is dissolved in the electrolyte. The invention is alsoapplicable to electrochemical fluorination processes wherein thefeedstock is bubbled into the electrolyte through a porous anode. In apresently preferred electrochemical fluorination process, to which theinvention is particularly applicable, a current-conducting essentiallyanhydrous hydrogen fluoride electrolyte is electrolyzed in anelectrolysis cell provided with a cathode and a porous anode (preferablyporous carbon), and the feedstock is introduced into the pores of saidanode and fluorinated within said pores.

Briefly, said preferred electrochemical fluorination process comprisespassing the feedstock to be fluorinated into the pores of a porousanode, e.g., porous carbon, disposed in a currentconducting essentiallyanhydrous hydrogen fluoride electrolyte such as KF- 2 HF. Said feedstockcontacts the fluorinating species within the pores of the anode and istherein at least partially fluorinated. Generally speaking, saidfluorination can be carried out at temperatures within the range of from80 to 500 C. at which the vapor pressure of the electrolyte is notexcessive. A preferred temperature range is from about 60 to 120 C.Pressures substantially above or below atmospheric can be employed ifdesired. Generally speaking, the process is conveniently carried out atsubstantially atmospheric pressures. The feedstock to be fluorinated ispreferably introduced into the pores of the anode at a rate such thatthere is established a pressure balance within the pores of the anodebetween the feedstock entering the pores of electrolyte attempting toenter said pores from another and opposing direction. Said feedstockflow rate can be within the range of from 3 to 600 milliliters perminute per square centimeter of anode cross-sectional area, takenperpendicular to the direction of flow and expressed in terms of gaseousvolume calculated at standard conditions. Current densities employed canbe within the range of 30 to X 1,000 preferably 50 to 500, milliamps persquare centimeter of anode geometric surface area. Typical voltagesemployed can range from 4 to 12 volts. Converted and unconvertedproducts are withdrawn from the pores of the anode and the productsrecovered from a cell effluent stream.

Further details of said preferred electrochemical fluorination processcan be found in copending application Ser. No. 683,089, filed Nov. 2,1967, by H. M. Fox and F. N Ruehlen, now U.S. Pat. No. 3,511,760.

Referring now to the drawing, the invention will be more fullyexplained. In the drawing there is illustrated one presently preferredtype of electrolytic cell, denoted generally by the reference numeral10, comprising a cell body 12 having an anode 14 disposed therein. Ashere illustrated, said anode comprises a cylinder of porous carbon 16having a core of an essentially impervious carbon 18 disposed therein.The walls of said cylinder of porous carbon extend below the bottom ofthe core of impervious carbon to form the cavity 20 in the bottom of theanode. A current collector 22, comprising a hollow metal conduit, suchas copper, is disposed within said core of imperviouscarbon and extendstherethrough to a point adjacent the bottom thereof. A plastic feedconduit 26 is mounted inside said current collector and extendstherethrough into communication with said cavity 20. Said currentcollector 22 is connected by means of lead 28 to the anode bus of thecurrent supply Preferably, the upper end of said anode l4 extends aboveelectrolyte level 30. A circular 32, here shown to be a cylinder ofcarbon steel perforated at its upper end portion, surrounds said anodel4 and is connected to the cathode bus of the current supply by asuitable lead wire 34. Any suitable source of current and connectionsthereto can be employed in the practice of the invention. Said anode 14can comprise any suitable type of anode which comprises a nonwettingporous element, preferably porous carbon. Said cell contains a suitableelectrolyte, e.g., KF' 2 HF. Examples of other anode structures whichcan be used in the practice of the invention are disclosed and claimedin copending application Ser. No. 680,123, filed Nov. 2, 1967, by W. V.Childs, now U.S. Pat. No. 3,51 1,762.

1n the operation of the cell arrangement, a feedstock comprisingl,2-dichloroethane introduced via conduit 36, and another feedstockcomprising 1,1,2-trichloroethane introduced via conduit 38, are mixed inconduit 40 and passed via feed conduit 26 into cavity 20 of anode 14.Preferably, said feedstocks are premixed similarly as shown in thedrawing, prior to their introduction into the cell. However, it iswithin the scope of the invention to introduce said feedstockssimultaneously in other ways, e.g., separately but simultaneouslythrough separate conduits. Said mixed feedstock from conduit 26 forms agas cap in cavity 20, i.e., displaces a portion of the electrolytetherefrom, and the feedstock enters the pores of the porous section 16of the anode, travels upward through the pores of said anode, and exitsfrom the upper end of the anode above electrolyte level 30. Duringpassage through the pores of said anode, at least a portion of saidfeedstock is electrochemically fluorinated. Fluorinated products,together with hydrogen and remaining unconverted feedstock, and possiblysome electrolyte vapors, are withdrawn from the space above theelectrolyte within the cell 12 via conduit 42 and passed into separationzone 44. Said separation zone can comprise any suitable means for theseparation of the materials in the cell effluent stream. For example,said cell effluent stream can be passed through a condenser and knockoutdrum, or other means for removing HF, and then passed through a suitableseries of fractional distillation columns. Recovered hydrofluoric acidelectrolyte is returned to the cell via conduit 46. An end productstream comprising monochloropentafluoroethane is withdrawn via conduit48. A second end product stream comprising 1,2-dichlorotetrafluoroethaneis withdrawn via conduit 50. A third end product stream comprisingl,l,2-trichloro-l,2,2-trifluoroethane is withdrawn via conduit 52. Astream of monochlorofluoroethanes comprising l-chlorol l,2,2-tetrafluoroethane; l-chlorol ,2,2- trifluoroethane; andl-chloro-2,2-difluoroethane is withdrawn via conduit 54 and passed intoconduit 40 for recycle to the cell. Said monochlorofluoroethanes willfluorinate to said end product monochloropentafluoroethane upon beingrecycled. A stream of dichlorofluoroethanes comprising l,2-dichloro-1,2,2-trifluoroethane; l,2-dichloro-l l difluoroethane; l,2dichlorol,2-difluoroethane; and l ,2-dichlorol fluoroethane is withdrawn viaconduit 56 and passed into conduit 40 for recycle to the cell. Saiddichlorofluoroethanes will fluorinate to said end productl,2-dichlorotetrafluoroethane upon being recycled. Unreactedl,2-dichloroethane can be recycled with said dichlorofluoroethanes. Astream of trichlorofluoroethanes comprising 1 ,l ,2-trichloro-2,2-difluoroethane; l,2,2-trichloro-2-fluoroethane; and 1,1,2-trichloro-2-fluoroethane is withdrawn from separation zone 44 viaconduit 58 and passed into conduit 40 for recycle to the cell. Saidtrichlorofluoroethanes will fluorinate to said end product1,1,2-trichloro-1,2,2trifluoroethane upon being recycled. Unreacted l, l,2-trichlorethane can be recycled with said trichlorofluoroethanes. Astream of light ends comprising chlorofluoroethanes is withdrawn viaconduit 60. A stream comprising l,l,2,2,-tetrachlorodifluoroethane andl,1,2,2- tetrachlorofluoroethane, together with heavy ends, e.g.,dimers, is withdrawn from separation zone 44 via conduit 62. Thebyproduct hydrogen is also withdrawn from the system by a conduit notshown. The amount of fresh makeup l,2- dichloroethane feedstockintroduced via conduit 36 and the amount of fresh 1,1,2-trichloroethanefeedstock introduced via conduit 38 can be adjusted in accordance withthe amounts thereof in said recycle streams so as to maintain thedesired ratio of said feedstocks.

The following examples will serve to further illustrate the invention.

EXAMPLES A series of runs was carried out for the electrochemicalfluorination of 1,2-dichloroethanc and l.l.2-trichloroethane.individually, and in admixture. The fluorination runs were carproduct.i.e.. which will fluorinate to said end product upon being recycled tothe electrochemical fluorination cell. The most desired and theprincipal products of the process are: 1,2-dichlorotetrafluoroethane andl, l .Z-trichlorol ,2.2-

ried out in a cell embodying the essential features of the cell il- 5lrifllforoethanfi Therefore. for p rposes of illustrating th lustratedin the drawing. The anode 14 had an outside diamef the y'elds f' beenreported terms of Said P ter of approximately 4 inches and the porouscarbon section c'pal proflucts and precursors I 16 thereof had a wallthickness of approximately l inch. The Refemng to the f table be noted mRuns 1 porous carbon employed in Said anode was a Commercial and 2 wherel,l .2-tr1chloroethane was charged alone as the grade designated as pC45 having a pore volume of abom feedstock the yields of A(dichlorofluoroethanes) plus B XO.5 cc. per gram with pore diametersranging from 10 to 100 (mchlomfluomethanes)- moles Pf" 100 moles of feedmicrons. The average pore diameter was about 58 microns. reacted f andrespecmel)" Rims 3 and 4 The eiecu-olyte employed was essentiallyanhydrous quid where l 2-dichloroethane was charged alone as thefeedstock hydrogen fluoride containing potassium fluoride as conductheWelds of A P B, moIes P 5 100 moles of feedstock tivity additive in themolar ratio of KF 2 HF. Said anode was reacted and K f 61ml 7 immersedin said electrolyte to a depth f approximately 12 where the feedstockwas a mixture of said l,2-d1chloroethane inches. The feed rates employedwere such that the feedstock and lilvz'tl'lchloroethane the yields of AP moles P and fluorinated products traveled upwardly through the pores100 9 of feeds'tock reamed. were 1- and 1.6. of the anode and exitedtherefrom at the top of the anode P sald Runssand the oven! Yleld ofabove the level of the electrolyte. The cell effluent was A P" B hasbeen markedly mcl'eased- This was unexpected analyzed by conventionalmeans such as gas-liquid because the calculated yield of A plus B inRuns 5 and 6, calmatography and mass spectrography. Other operatingcondiculated on the basis of comparable runs wherein the convertions andthe results of the runs in terms of type and quantity W ntially he Same.was only 87.3 and 86.3. of products obtained are given in table 1 below.25 respectively. The date in table I also show that. in addition toTABLE I Run Number.. l 2 3 4 5 6 7 Cell temp, C. 100 00 105 96 100 10005 Current, amps 250 250 250 150 250 250 250 Voltage, volts T 3 7.5 7.37.5 7.3 7.3 7.6 Feed rate, ml./min./cm. (anode geometric surface area):

Trichloroetharie. 1.80 1.91 Dichloroetharie. 1. 77 2. 10 Total mixture..1.52 2.17 2.13 Feed rate, ml./min./cm. (anode cross section area):

Trichloroethane. 34.0 35.0 Dichloroethane... 33.4 30.6

Total mixutre. 28. 7 41. 0 40. 2 Feed rate, moles/hr.;

Trichloroethane. 4. 4.76 1.15 2.12 2.09 Dichloroethane.. 4.42 5.21 2 643.20 3.22

Total... 4. 40 4. 75 4.42 5.21 3 70 5.41 5. 31

Feed converted, percent; 7

Trichloroethane. 42.3 37.7 33.2 28.3 24.8 Dichloroethane 37. 9 45.0 47.837. 0 35.0 Products, mole percent. I Monochlorofluoroethanes.. 1. 361.42 4.75 4.04 4.40 4. 27 3.80 (A) Dichlorofluoroethanes... 7.66 7.8080. 95 86.25 55.27 56.14 55. 42 (B) 'Irichlorofluoroethancs... 73.08 71.48 11.55 6. 86 33. 86 36.49 36.57 Tctrachlorofiuoroethanes. 11.94 12. 92Traci Trace 1. 39 1.80 1.78 Dimers. 5.00 5. 40 1. 2.52 2.00 1.22 1.07 Ccompounds. Trace 0.80 1.06 0.33 Truce 0.08 1.30 'IotaL. 1000010000100.00 100.00 100. 00 100. 00 100. 00

Yield of A+B, moles/100 moles of feed reacted. 76. 2 75.5 01. 4 01.000.3 01.5 01.0 Calculated I yield of A+B. moles! I 100 moles of feedreacted 1 87. 3 a 86. 3 I 85. 4

1 Calculated by combining products that would be obtained by reactingeach feedstock in the above table 1, the data are presented in terms ofmonochlorofluoroethane products. dichlorofluoroethane products,trichlorofluoroethane products, and tetrachlorofluoroethane products.The

increasing the yield of A plus B. the efficiency of the conversion ofl.l.2-trichloroethane to l.l,2-trichlorol .2,2- trifluoroethane and itsprecursors has been increased without any significant sacrifice in theefficiency of the conversion of l.2-dichloroethane tol.2-dichlorotetrafluoroethane and its precursors.

While certain embodiments of the invention have been described forillustrative purposes, the invention is not limited thereto. Variousother modifications or embodiments of the invention will be apparent tothose skilled in the art in view of this disclosure. Such modificationsor embodiments are within the spirit and scope of the disclosure.

I claim:

1. in an electrochemical fluorination process which comprises passing anelectric current through a current-conducting. essentially anhydrousliquid hydrogen fluoride electrolyte contained in an electrolytic cellprovided with a cathode and a porous anode, passing a feedstock l)comprising 12- dichloroethane into a said cell and into the pores of asaid anode therein, separately passing a feedstock (2) comprisingl,l,2-trichloroethane into a said cell and into the pores of a saidanode therein, fluorinating at least a portion of each said feedstockwithin said pores to fluorinated products including (a) 1,1,2-trichloro-l ,2,2-trifluoroethane and (b) 1.2-dichlorotetrafluoroethane, and recovering said products from a celleffluent stream, the improvement comprising: increasing the selectivityof said process for the total production of said products (a) and (b) bysimultaneously passing both of said feedstocks l) and (2) into the poresof the same said anode and therein fluorinating at least a portion ofsame to said products.

2. A process according to claim 1 wherein said two feedstocks1,1,2-trichloroethane and 1,2-dichloroethane are passed into said cellin a trichloroethane to dichloroethane mole ratio within the range of 0.l :l to 20: l.

3. A process according to claim 2 wherein said feedstocks are premixedprior to introduction into said cell.

4. A process according to claim 3 wherein the range of said ratio is0.3:1 to 5:1.

5. A process according to claim I wherein: said anode comprises a porouscarbon element; and said two feedstocks I l and (2) are introduced intothe pores of said porous carbon element and are therein at leastpartially fluorinated to said products.

6. A process according to claim 5 wherein: said feedstocks areintroduced at a total feed rate within the range of from 3 to 600milliliters per minute per square centimeter of porous carboncross-sectional area; said fluorination is carried out at a celltemperature within the range of from about 60 to about C.; the currentdensity employed is within the range of from 50 to 500 milliamps persquare centimeter of porous carbon anode geometric surface area; saidcell effluent stream is passed to a products separation zone; a firstproduct stream comprising 1.1.2-trichloro-l ,2.2-trifluoroethane iswithdrawn from said products separation zone; a second product streamcomprising l.2-dichlorotetrafluoroethane is withdrawn from said productsseparation zone; a first recycle stream comprising unreactedl,2-dichloroethane and dichlorofluoroethanes which are precursors forand will fluorinate to said 1,2- dichlorotetrafluoroethane product iswithdrawn from said separation zone and recycled to said cell; and asecond recycle stream comprising unreacted I, l ,Z-trichloroethane andtrichlorofluoroethanes which are precursors for and will fluorinate tosaid 1,1 ,2-trichloro-l,2.2 -trifluoroethane product is withdrawn fromsaid separation zone and recycled to said cell.

7. A process according to claim 6 wherein said two feedstocks 1, l,Z-trichloroethane and LZ-dichloroethane are passed into the pores ofsaid porous carbon anode in a trichloroethane to dichloroethane moleratio within the range offrom().l;l to 20:].

8. A process according to claim 7 wherein: the range of said ratio is0.3:] to 5:1; the amount of fresh feedstocks (I) and (2) introduced intothe cell is adjusted in accordance with the amount of said feedstocks insaid first and second recycle streams so as to maintain said ratiowithin said range; and said feedstocks l and (2 l, and said first andsecond recycle streams are premixed prior to introduction into saidcell.

i i i l i

2. A process according to claim 1 wherein said two feedstocks 1,1,2-trichloroethane and 1,2-dichloroethane are passed into said cell ina trichloroethane to dichloroethane mole ratio within the range of 0.1:1to 20:1.
 3. A process according to claim 2 wherein said feedstocks arepremixed prior to introduction into said cell.
 4. A process according toclaim 3 wherein the range of said ratio is 0.3:1 to 5:1.
 5. A processaccording to claim 1 wherein: said anode comprises a porous carbonelement; and said two feedstocks (1) and (2) are introduced into thepores of said porous carbon element and are therein at least partiallyfluorinated to said products.
 6. A process according to claim 5 wherein:said feedstocks are introduced at a total feed rate within the range offrom 3 to 600 milliliters per minute per square centimeter of porouscarbon cross-sectional area; said fluorination is carried out at a celltemperature within the range of from about 60* to about 120* C.; thecurrent density employed is within the range of from 50 to 500 milliampsper square centimeter of porous carbon anode geometric surface area;said cell effluent stream is passed to a products separation zone; afirst product stream comprising 1,1, 2-trichloro-1,2,2-trifluoroethaneis withdrawn from said products separation zone; a second product streamcomprising 1,2-dichlorotetrafluoroethane is withdrawn from said productsseparation zone; a first recycle stream comprising unreacted1,2-dichloroethane and dichlorofluoroethanes which are precursors forand will fluorinate to said 1,2-dichlorotetrafluoroethane product iswithdrawn from said separation zone and recycled to said cell; and asecond recycle stream comprising unreacted 1,1,2-trichloroethane andtrichlorofluoroethanes which are precursors for and will fluorinate tosaid 1,1,2-trichloro-1,2,2-trifluoroethane product is withdrawn fromsaid separation zone and recycled to said cell.
 7. A process accordingto claim 6 wherein said two feedstocks 1, 1,2-trichloroethane and1,2-dichloroethane are passed into the pores of said porous carbon anodein a trichloroethane to dichloroethane mole ratio within the range offrom 0.1:1 to 20:1.
 8. A process according to claim 7 wherein: the rangeof said ratio is 0.3:1 to 5:1; the amount of fresh feedstocks (1) and(2) introduced into the cell is adjusted in accordance with the amountof said feedstocks in said first and second recycle streams so as tomaintain said ratio within said range; and said feedstocks (1) and (2),and said first and second recycle streams, are premixed prior tointroduction into said cell.